1. Field of the Invention
This invention relates to a remote-controlled automatic control apparatus, such as a security apparatus or a keyless entry apparatus for a vehicle, and a data transmission method for the apparatus. More particularly, the present invention relates to a remote-controlled automatic control apparatus and a data transmission method for preventing a breach of security of the apparatus using a copying device such as a learning remote controller.
1. Description of the Related Art
A security system for protecting a motor vehicle and using a remote-control unit are known. Such a security system prevents burglary or theft by sounding a siren and/or turning on and off the head lamps of the vehicle as well as inhibiting the vehicle from being started and driven by starter cutting (for inhibition of engine starting) or fuel supply interruption, if a person other than the owner or user of the vehicle opens a door of the vehicle, or makes a certain impact on the vehicle, or opens the trunk, when the security system is armed.
Such security systems include a type using a portable transmitting unit (remote control unit) for starting and stopping the security operation. Starting the security operation (arming) or stopping the security operation (disarming) is effected by pressing an arming key or disarming key provided on the transmitting unit.
In such a security system, data transmitted from the transmitting unit has a predetermined identification (ID) code and can only arm or disarm a motor vehicle provided with a main security unit having the same ID code. Accordingly, one main unit cannot be armed or disarmed by a transmitting unit whose ID code is different from the ID code provided in the main unit. Thus the security system is arranged to have a special motor vehicle burglarproof function.
In this conventional security system, however, the ID code included in the data transmitted from the transmitting unit is fixed. Therefore, it is possible to prepare a transmitting unit falsely identifiable as the genuine transmitting unit by using a "copying machine" (such as a "learning" remote controller) to copy data transmitted from the genuine transmitting unit. The possibility of such wrongful copying reduces the effectiveness of the security system.